U.S. patent number 11,197,695 [Application Number 16/055,691] was granted by the patent office on 2021-12-14 for receiving part and instrument for holding the receiving part.
This patent grant is currently assigned to BIEDERMANN TECHNOLOGIES GMBH & CO. KG. The grantee listed for this patent is BIEDERMANN TECHNOLOGIES GMBH & CO. KG. Invention is credited to Timo Biedermann, Dimosthenis Dandanopoulos.
United States Patent |
11,197,695 |
Biedermann , et al. |
December 14, 2021 |
Receiving part and instrument for holding the receiving part
Abstract
A receiving part of a bone anchoring device includes a channel
adjacent a first end for receiving a bone fixation element, the
channel forming two free legs each having an engagement structure
for engaging a locking element to lock the bone fixation element in
the channel, an outer surface portion, and at least one projection
for engaging an instrument to connect the instrument to the
receiving part. The projection projects radially outwardly from the
outer surface portion, is spaced apart axially from the first end
of the receiving part, and has a circumferential width less than a
circumferential width of the legs. The projection has a first side
wall that faces the first end. At least part of the first side wall
is inclined towards the first end as the first side wall extends
circumferentially, to form a region of the projection that narrows
towards the first end.
Inventors: |
Biedermann; Timo (Trossingen,
DE), Dandanopoulos; Dimosthenis (VS-Schwenningen,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
BIEDERMANN TECHNOLOGIES GMBH & CO. KG |
Donaueschingen |
N/A |
DE |
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Assignee: |
BIEDERMANN TECHNOLOGIES GMBH &
CO. KG (Donaueschingen, DE)
|
Family
ID: |
59569229 |
Appl.
No.: |
16/055,691 |
Filed: |
August 6, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190046240 A1 |
Feb 14, 2019 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62542674 |
Aug 8, 2017 |
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Foreign Application Priority Data
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Aug 8, 2017 [EP] |
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17185421 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
17/7076 (20130101); A61B 17/7032 (20130101); A61B
17/7086 (20130101); A61B 17/866 (20130101) |
Current International
Class: |
A61B
17/70 (20060101); A61B 17/86 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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103431903 |
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Dec 2013 |
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CN |
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10 2013 100574 |
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Jul 2014 |
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DE |
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3 120 791 |
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Jan 2017 |
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EP |
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102202589 |
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Sep 2011 |
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GN |
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2013/034351 |
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Mar 2013 |
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WO |
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Other References
Extended European Search Report for Application No. 17185421.9,
dated Feb. 9, 2018, 11 pages. cited by applicant.
|
Primary Examiner: Plionis; Nicholas J
Attorney, Agent or Firm: Lewis Roca Rothgerber Christie
LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION(S)
The present application claims priority to and the benefit of U.S.
Provisional Patent Application No. 62/542,674, filed Aug. 8, 2017,
the contents of which are hereby incorporated by reference in their
entirety, and claims priority from European Patent Application EP
17 185 421.9, filed Aug. 8, 2017, the contents of which are hereby
incorporated by reference in their entirety.
Claims
What is claimed is:
1. A receiving part of a bone anchoring device, the receiving part
having a first end, a second end opposite to the first end, and a
central axis extending through the first end and the second end,
and comprising: a channel adjacent to the first end for receiving a
bone fixation element, wherein the channel forms two free legs each
having an engagement structure for engaging a locking element to
lock the bone fixation element in the channel; an outer surface
portion that faces away from the central axis; and at least one
projection configured to engage an engagement recess of an
instrument to provide a connection between the instrument and the
receiving part, wherein the at least one projection projects
radially outwardly from the outer surface portion, is spaced apart
axially from the first end of the receiving part, is spaced apart
circumferentially from the channel on one side by a first region of
the outer surface portion, and is spaced apart circumferentially
from the channel on an opposite side by a second region of the
outer surface portion, and has an outwardly facing surface with at
least a portion having a same contour as the first and second
regions of the outer surface portion when viewed in a cross-section
perpendicular to the central axis; wherein the at least one
projection comprises a first side wall that faces and is inclined
relative to the first end as the first side wall extends
circumferentially around the central axis to form a region of the
at least one projection that widens as the at least one projection
extends axially away from the first end, and a lower side wall that
faces the second end of the receiving part, wherein an entire
circumferential width of the lower side wall extends
circumferentially around the receiving part at a constant axial
height of the receiving part.
2. The receiving part according to claim 1, wherein the at least
one projection and the engagement recess of the instrument are
configured to engage in a form-fit engagement.
3. The receiving part according to claim 1, wherein the at least
one projection has a triangular shape when viewed in a direction
perpendicular to the central axis.
4. The receiving part according to claim 1, wherein at least part
of the outer surface portion of the receiving part around the at
least one projection and at least part of the outwardly facing
surface of the at least one projection have cylindrical
contours.
5. The receiving part according to claim 1, wherein the at least
one projection further comprises a second side wall that is
inclined towards the first end as the second side wall extends
circumferentially around the central axis, and wherein the first
and second side walls are configured to guide and align the
instrument when the instrument is attached to the receiving
part.
6. The receiving part according to claim 5, wherein the first and
second side walls are symmetric with respect to each other about an
axis parallel to the central axis.
7. The receiving part according to claim 5, wherein the first and
second side walls converge at a tip portion of the at least one
projection that faces the first end of the receiving part.
8. The receiving part according to claim 1, wherein the lower side
wall is provided with an undercut.
9. The receiving part according to claim 1, wherein the at least
one projection comprises two projections, with one of the
projections being provided on each of the legs.
10. A receiving part of a bone anchoring device, the receiving part
having a first end, a second end opposite to the first end, and a
central axis extending through the first end and the second end,
and comprising: a channel adjacent to the first end for receiving a
bone fixation element, wherein the channel forms two free legs each
having an engagement structure for engaging a locking element to
lock the bone fixation element in the channel; an outer surface
portion that faces away from the central axis; and at least one
projection configured to engage an engagement recess of an
instrument to provide a connection between the instrument and the
receiving part, wherein the at least one projection projects
radially outwardly from the outer surface portion, is spaced apart
axially from the first end of the receiving part, and has a
circumferential width that is less than a circumferential width of
each of the legs; wherein the at least one projection comprises an
outwardly facing surface with an outer perimeter, where less than
half of the entire outer perimeter is chamfered, a first side wall
that faces and is inclined relative to the first end as the first
side wall extends circumferentially around the central axis to form
a region of the at least one projection that widens as the at least
one projection extends axially away from the first end, and a lower
side wall that faces the second end of the receiving part, wherein
an entire circumferential width of the lower side wall extends
circumferentially around the receiving part at a constant axial
height of the receiving part.
11. A system comprising the receiving part according to claim 10
and the instrument, the instrument comprising a holding member
configured to hold the receiving part, wherein the holding member
comprises a first arm and a second arm that are movable relative to
each other between an open position in which the receiving part is
insertable between the first arm and the second arm, and a closed
position in which the receiving part is configured to be held
between the first arm and the second arm, and wherein at least one
of the first arm or the second arm comprises the engagement recess
configured to engage the at least one projection of the receiving
part.
12. The system according to claim 11, wherein the holding member is
tubular.
13. The system according to claim 11, wherein a guiding channel
comprising opposing side walls is formed at an inner wall portion
of each of the first and second arms, and wherein the guiding
channel extends between a free end of a respective one of the arms
and the engagement recess of the respective arm, and is configured
to guide the at least one projection to the engagement recess.
14. The system according to claim 13, wherein when the at least one
projection is positioned in the guiding channel, the arms are
expanded into the open position, and wherein when the at least one
projection is received in the engagement recess, the arms assume
the closed position.
15. The system according to claim 13, wherein a bottom surface of
the guiding channel is inclined with respect to a central axis of
holding member, such that the inclined bottom surface is engageable
with the chamfer on the at least one projection to guide the at
least one projection to the engagement recess.
16. The system according to claim 11, wherein the inner wall
portion of the arms is provided with a cylindrical contour which
mates with a cylindrical contour of the receiving part.
17. A method of connecting a receiving part of a bone anchoring
device to an instrument, the receiving part having a first end, a
second end opposite to the first end, and a central axis extending
through the first end and the second end, and comprising a channel
adjacent to the first end for receiving a bone fixation element,
wherein the channel forms two free legs each having an engagement
structure for engaging a locking element to lock the bone fixation
element in the channel, an outer surface portion that faces away
from the central axis, and at least one projection that projects
radially outwardly from the outer surface portion, that is spaced
apart axially from the first end of the receiving part, is spaced
apart circumferentially from the channel on one side by a first
region of the outer surface portion, and is spaced apart
circumferentially from the channel on an opposite side by a second
region of the outer surface portion, and that has an outwardly
facing surface with at least a portion having a same contour as the
first and second regions of the outer surface portion when viewed
in a cross-section perpendicular to the central axis, wherein the
at least one projection comprises a first side wall that faces and
is inclined relative to the first end as the first side wall
extends circumferentially around the central axis to form a region
of the at least one projection that widens as the at least one
projection extends axially away from the first end, and a lower
side wall that faces the second end of the receiving part, wherein
an entire circumferential width of the lower side wall extends
circumferentially around the receiving part at a constant axial
height of the receiving part, the instrument comprising a holding
member comprising a first arm, a second arm, and an engagement
recess at at least one of the first or second arms, the method
comprising: advancing the first arm and the second arm over the
first end of the receiving part to insert the receiving part
therebetween while the first arm and the second arm are in an open
position; further advancing the receiving part into the holding
member until the at least one projection of the receiving part
engages the engagement recess of the instrument, while the first
arm and the second arm assume a closed position to hold the
receiving part therebetween, thereby connecting the instrument to
the receiving part.
Description
BACKGROUND
Field
The invention relates to a receiving part of a bone anchoring
device, to an instrument for use with the receiving part in
surgery, and to a system including the instrument and the receiving
part. Such a receiving part is generally configured to connect a
fixation element such as a rod with an anchoring element that can
be inserted in a bone. The receiving part may be a separate member
or it may be integrally formed with the anchoring element. The
instrument is adapted to hold the receiving part in various
applications before and/or during surgery, and may therefore be
embodied, e.g., as an approximator, an extension device, a head
placer, a reduction tool, etc.
Description of Related Art
A system for introducing an elongated spinal rod to a head of a
monoaxial bone fastener device is known, for example, from US
2006/0025768 A1. The head includes a top surface, a bottom surface,
and a U-shaped channel defining two legs. Each of the legs has two
lateral end faces facing the channel. Recesses are formed in the
end faces to define a seat for secure engagement with an instrument
for handling the bone fastener or for introducing the spinal rod
into the U-shaped channel. Also, an outer surface portion of each
leg sidewall is provided with a curved shoulder which defines an
arc-shaped cavity configured to receive a portion of another
instrument for holding the head.
U.S. Pat. No. 8,267,969 B2 discloses a screw system for use in
stabilization of bone structures. The screw system includes a
screw, a retaining ring, a coupler, and a seat which receives the
rod in a rod channel. On the outside surface of the seat, a flange
is formed adjacent a top end of the seat. The flanges extend along
the entire length of the legs in the circumferential direction. The
flanges and/or the recesses allow gripping the seat using an
instrument.
U.S. Pat. No. 6,540,748 B2 discloses a surgical screw system,
wherein the U-shaped channel defines two lateral legs at a receiver
member. Adjacent a top end of the receiver member, a flange extends
at the legs along the entire length in the circumferential
direction.
U.S. Pat. No. 8,025,683 B2 describes a surgical implant having a
head with spaced-apart posts. A rod receiving area juxtaposes the
posts. Each post has an outward side face having a vertically
extending cylindrical surface adjacent a top end from which a
generally inwardly directed undersurface extends in a
circumferential direction. A cylindrical recess or bore penetrates
the undersurface and is torsionally engageable with an inward
facing tubular protrusion of a surgical tool.
U.S. Pat. No. 8,998,958 B2 describes a locking device introducer
instrument for a rod fixation assembly. A receiver for receiving
the rod is provided with an annularly extending flange at its legs
which is penetrated by a release aperture that allows releasing of
a locking ring retained in a groove formed at an inner bore of the
receiver.
U.S. Pat. No. 9,005,260 B2 describes a receiver body for a spinal
fixation system. Flanges extend circumferentially at each of the
legs at a distance from the top end of the receiver body, wherein
each flange is provided with two circular segments and a flat
segment in which a radial bore is formed that provides for a pivot
attachment point for external instruments. Further, one of the
flanges is provided with an axial cutout or channel. A mechanism is
thus provided for locking the radial position of the instrument
after the instrument's attachment members are passed over the flat
segments and rotated or "twisted" around beneath the circular
segments. After the instrument is twisted over the circular
segment, a pin or nail protuberance on the instrument can be
inserted or engaged with the axial cutout or channel to lock the
radial position of the instrument on the receiver body.
SUMMARY
It is an object of the present invention to improve the connection
between a receiving part and an instrument for holding the
receiving part, and/or to improve the ease of an attachment process
of the instrument to the receiving part.
According to embodiments of the invention, a receiving part is
provided which includes at least one projection, preferably two
projections at opposed locations, at an outer surface portion
thereof. The projection is configured to be engaged by a mating
engagement recess formed at an instrument for holding the receiving
part. A form-fit connection between the instrument and the
receiving part is achieved by the engagement. Moreover, the
projection includes a shape which tapers in a direction towards the
top end of the receiving part. As a consequence, when an instrument
is to be attached to the receiving part, wherein the projection of
the receiving part is to be received by a corresponding recess of
the instrument, the tapered shape of the projection allows for a
self-alignment of the instrument with respect to the receiving
part, and thus allows guiding of the instrument into the correct
position and posture before establishing the form-fit connection.
The tapered shape thus supports and improves the attachment
process.
Moreover, the tapered shape allows for a unique spatial structure
of the projection, which provides for a form-fit connection between
the receiving part and the instrument, thereby securing the spatial
orientation of the instrument with respect to the receiving part
during a holding operation.
Still further, by providing a projection at the side of the
receiving part which is received in a recess at the side of an
instrument, a particular advantage arises in that less space is
available for body tissue or fluids to accumulate in hidden corners
at the receiving part. The projection is exposed to the outside,
and the tissue and/or fluids may not easily adhere to the
projection in considerable amounts as compared with, e.g., a
recessed structure. Accordingly, the ease of surgical operations is
improved.
The shapes of the projection of the receiving part and of the
recess at the instrument need not be identical. Rather, the
dimension of the projection (e.g., in plan-view) can be smaller
than that of the recess of the instrument, as long as a form-fit
connection is maintained and a mutual translation and rotation is
ruled out. Nevertheless, a small amount of tolerance or play may be
acceptable to allow for easily finding a correct orientation of the
instrument with respect to the receiving part, or to allow tissue
and/or fluids to escape during attachment.
In more specific embodiments, the projection may have a triangular
shape, wherein for example two side walls extend towards the top
end of the receiving part in an inclined manner, thereby
approaching each other adjacent a top corner of the triangular
shape. An opposite side wall faces the bottom end of the receiving
part. A projection having such a shape provides for a simple
structure, is easy to manufacture, establishes an efficient
tapering structure, and guarantees a stable form-fit connection.
The side walls of the triangular shape may also be planar, or may
be concavely or convexly curved. Also, the corners of the triangle
may be more or less rounded, or even cut off, to avoid sharp tips.
The side walls, in particular the side wall facing the bottom end
of the receiving part, may be undercut to improve the connection
between the projection and the recess at the instrument.
According to further embodiments of the invention, an instrument is
provided which is configured to hold the receiving part as
described above. Such an instrument may for example be an
approximator, a head placer, a rod reducing tool, a head extension
device, or the like, and the invention is not limited to the
specific application or use of the instrument. The instrument
includes a tubular holding member and may or may not include
further members, e.g., further tubular members or sleeves guided by
the holding member to perform a specific application. Drive
mechanisms and/or coupling members for driving the one or more
tubular members may also be provided.
The tubular holding member holds the receiving part via an
engagement recess which is configured and shaped to receive the
projection of the receiving part as indicated above. The holding
member may have a first arm and a second arm that are movable
relative to each other, between an open position in which the
receiving part is insertable between the first arm and the second
arm, and a closed position in which the receiving part is held
between the first arm and the second arm. The direction of movement
between the arms may include an expansion or spreading of the arms.
In one embodiment, the expansion may originate from a rotation of
the arms about a pivot point arranged at a distance from the distal
ends of the arms.
According to specific embodiments, a guiding channel forming side
walls on the arms may be arranged at the distal end of one arm or
both arms. The guiding channel extends from the distal end up to
the engagement recess, and serves to align the instrument with the
receiving part and to guide the projection therethrough and into
the engagement recess.
The side walls of the guiding channel face each other and are
arranged to abut on respective side walls of the projection of the
receiving part which approach each other in a direction towards the
top end of the receiving part. Due to the resulting inclination of
the side walls of the projection with respect to an axis parallel
to a central axis of the receiving part, which is also
substantially the axis along which the instrument approaches and
engages the receiving part, a respective side wall of the guiding
channel experiences a rotational force while sliding down along the
corresponding side wall of the projection. The instrument is
thereby rotated and aligned during the sliding contact, such that
the projection enters the guiding channel and eventually enters the
engagement recess formed at a distance from the distal ends of the
arms.
In a more specific embodiment, a base or bottom surface of the
guiding channel extending between the side walls is inclined with
respect to a central axis of the tubular holding member. This
allows for a smooth expansion of the arms until the projection
snaps into the engagement recess of the instrument to establish the
form-fit connection.
BRIEF DESCRIPTION OF THE DRAWINGS
Further aspects and advantages will become apparent by a detailed
explanation of embodiments when taken in conjunction with the
appended drawings. In the drawings:
FIG. 1 shows a perspective view of a polyaxial bone anchoring
device including a receiving part, according to a first embodiment
of the invention;
FIG. 2 shows an enlarged view of the bone anchoring device of FIG.
1 in an assembled state;
FIG. 3 shows a cross-sectional view of the bone anchoring device
shown in FIG. 2;
FIG. 4A shows a perspective view of the receiving part of the first
embodiment, from a top perspective;
FIG. 4B shows a perspective view of the receiving part of the first
embodiment, from a bottom perspective;
FIG. 5A shows a side view of the receiving part according to the
first embodiment;
FIG. 5B shows a top view of the receiving part according to the
first embodiment;
FIG. 6 shows a cross-sectional view of the receiving part of the
first embodiment, the cross-section taken along line A-A in FIG.
5B;
FIG. 7 shows a perspective view of an embodiment of an
instrument;
FIG. 8A shows a cross-sectional view of the instrument shown in
FIG. 7;
FIG. 8B shows a lateral side view of the instrument shown in FIG.
7;
FIG. 9 shows the instrument of FIG. 7 attached to the receiving
part of the first embodiment in a lateral side view;
FIG. 10 shows a cross-sectional view of the receiving part and
instrument shown in FIG. 9, the cross-section taken along line B-B
in FIG. 9;
FIG. 11A shows, in a perspective view, a first state of attaching
the instrument to the receiving part according to the first
embodiment;
FIG. 11B shows, in a perspective view, a second state of attaching
the instrument to the receiving part according to the first
embodiment;
FIG. 11C shows, in a perspective view, a third state of attaching
the instrument to the receiving part according to the first
embodiment;
FIG. 12A shows, in a cross-sectional view, the first state of
attaching the instrument to the receiving part according to the
first embodiment;
FIG. 12B shows, in a cross-sectional view, the second state of
attaching the instrument to the receiving part according to the
first embodiment;
FIG. 12C shows, in a cross-sectional view, a further state between
the second state and the third state of attaching the instrument to
the receiving part according to the first embodiment;
FIG. 12D shows, in a cross-sectional view, the third state of
attaching the instrument to the receiving part according to the
first embodiment;
FIG. 13 shows a perspective view of a second embodiment of a
receiving part which is formed integrally with an anchoring element
in a monoaxial bone anchoring device;
FIG. 14 shows a cross-sectional view of the bone anchoring device
of FIG. 13;
FIG. 15A shows the instrument attached to the receiving part
according to the first embodiment in a side view;
FIG. 15B shows a modified embodiment of an instrument attached to a
receiving part in a side view;
FIG. 15C shows a further modified embodiment of an instrument
attached to a receiving part in a side view;
FIG. 15D shows another further modified embodiment of an instrument
attached to a receiving part in a side view;
FIG. 15E shows yet another further modified embodiment of an
instrument attached to a receiving part in a side view.
DETAILED DESCRIPTION
With reference to FIGS. 1-6, a first embodiment of a receiving part
5 is described. FIGS. 1 and 2 provide an overview of a polyaxial
bone anchoring device 200 which includes the receiving part 5. The
bone anchoring device 200 further includes an anchoring element 1
having a head 3, a shank 2 provided with a bone thread for
anchoring in a bone, a pressure element 6 adapted to exert pressure
onto the head 3 when assembled in the receiving part 5, and a
locking element 7 that has an external thread 71 for cooperating
with an internal thread 54 of the receiving part 5 in order to
exert pressure onto a spinal fixation element 100 received in the
receiving part 5 and/or the pressure element 6. In this embodiment,
the external thread 71 is a flat thread and the locking element 7
is further provided with an engagement feature 72, which may be
hex-shaped, torx-shaped, or otherwise shaped as known in the art.
The locking element 7 is herein provided as a single piece
setscrew, but modified embodiments may also include other kinds of
locking elements such as dual inner screws, etc.
The pressure element 6 has a seat for receiving the spinal fixation
element 100 and two upwardly extending flexible legs, with each leg
having a laterally protruding flange at its free end which allows
for latching-in into corresponding recesses provided in the inner
bore 51 of the receiving part 5 to prevent a further upward
movement of the pressure element in the receiving part, when the
head 3 of anchoring element 1 is inserted through a bottom opening
53 of the receiving part into an accommodation space 52 of the
receiving part 5.
The pressure element 6 is further provided with a
spherically-shaped recess at its bottom side configured to receive
the spherical head 3 of the anchoring element 1. Flexible flanges
extend at the distal end of the pressure element, which may extend
around a maximum diameter portion of the spherical head 3 in order
to frictionally clamp the head when it is introduced into the
accommodation space 52 of the receiving part 5 and pressed against
the pressure element 6, which in turn is prevented from an upward
movement by the engagement between the legs of the pressure element
and the latching recess of the receiving part. The accommodation
space 52 has an increased width as compared with the substantially
cylindrical bore 51 of the receiving part 5, in order to allow
expansion of the flanges during insertion of the head 3.
It is noted that modified embodiments of the invention may include
other types of pressure elements, and the invention is not limited
to the specific kind of pressure element. In specific embodiments,
a pressure element may even be omitted.
With reference to FIGS. 4A-6, the receiving part 5 is described in
more detail. The receiving part 5 has a top or first end 5a and a
bottom or second end 5b, and a substantially cylindrical bore 51
extends from the first end 5a in a direction towards the second end
5b. The inner bore 51 is coaxial with a central axis C of the
receiving part 5 that extends through the first and second ends 5a,
5b. A channel 55 for receiving the spinal fixation element, which
may be U-shaped or V-shaped, extends from the first end 5a in a
direction towards the second end 5b. An axis D of the channel 55
extends perpendicular to the central axis C. The channel 55 defines
two free legs 56a, 56b at the receiving part 5.
The receiving part 5 has an outer surface portion 58 which has a
generally cylindrical contour. The term "generally" encompasses
minor deviations, such as a recessed flat portion beneath the
U-shaped channel 55 on each side of the receiving part 5 and
longitudinal grooves extending from the first end 5a at each of the
legs 56a, 56b in a direction parallel to the central axis C, as
shown in FIG. 5A, which are due to the shaping process of various
sidewalls of projection 50, to be described in greater detail
below.
As can best be seen in FIGS. 4A and 4B, the projection 50 is formed
on the outer surface portion 58 on each of the legs 56a, 56b of the
receiving part 5. In the plan-view onto the projection 50 in FIG.
5A, the projection 50 is provided with a substantially triangular
shape and is arranged symmetrical with respect to an axis parallel
to the central axis C. One corner 505 of the projection extends in
a direction toward the top or first end 5a and an opposite edge or
sidewall 502 faces the bottom or second end 5b. The projection 50
is formed with a top surface 501 extending parallel to the
cylindrical contour of the outer surface portion 58. The height of
the projection 50 with respect to the outer surface portion 58 is
less than a width of the projection 50 between a left-side corner
507 and a right-side corner 508 as measured in a circumferential
direction, and is less than a length of the projection 50 measured
between the top corner 505 and the opposite sidewall 502 facing the
bottom or second end 5b in a direction parallel to the central axis
C.
Further, a width between corners 507, 508 in a circumferential
direction is larger than a length of projection 50 between the top
corner 505 and the opposite sidewall 502 in a direction parallel to
the central axis C. The sharp tips at the left-side and right-side
corners 507, 508 are removed to create flattened corner profiles.
As will be described below with respect to the function of the
projection 50, the sidewall 502 facing the second end 5b is
provided with an undercut, as can best be seen in FIG. 6. In other
words, a surface of the sidewall 502 is inclined with respect to a
plane perpendicular to the central axis C. This undercut allows for
an improved form-fit connection between an instrument 60 (see
below) and the receiving part 5.
At the top corner 505 facing the first end 5a of the receiving part
5, a chamfer 506 is formed to yield a surface at the top corner 505
which is inclined with respect to the central axis C. This chamfer
increases a sliding contact area with respect to an instrument that
is attached to the receiving part 5. As a consequence, arms of the
instrument are smoothly spread and expanded by such contact.
As can particularly be seen in FIGS. 4A and 4B, the projections 50
are arranged at about a center of each leg, at a distance from the
first end 5a and the second end 5b in a direction parallel to the
central axis C, and with respect to each of the lateral end faces
of the legs 56a, 56b in a circumferential direction. In other
words, the dimensions of the projections 50 are smaller than those
of the legs 56a, 56b in both a direction parallel to the central
axis C and a circumferential direction. Further, the projections 50
are located opposite each other with respect to the central axis C,
and are arranged along an axis E, which is perpendicular to the
central axis C and the axis D of the channel 55, respectively, as
can be seen in FIG. 5B. It is noted that in modified embodiments,
the projections 50 may be arranged offset from a center position at
the legs, or may be positioned differently axially, for example,
closer to the bottom end of the receiving part 5 beneath the
legs.
With reference to FIGS. 4A, 5A, and 5B, the triangular structure of
the projection 50 leads to a taper that narrows towards the top or
first end 5a. Between the left-side corner 507 and the top corner
505 and between the right-side corner 508 and the top corner 505,
edges or sidewalls 503, 504 extend substantially radially from the
outer surface portion 58 of the receiving part 5. In this
embodiment, the sidewalls 503 and 504 are substantially planar and
terminate at the rounded structures of the corners 505, 507, and
508. Each of the sidewalls 503, 504 is inclined with respect to a
direction parallel to the central axis C. As will be explained
below, the sidewalls 503, 504 allow for a self-alignment of an
instrument that is guided towards and onto the receiving part 5.
The corner 505 spans an angle .alpha. of more than 90 degrees (see
FIG. 15A). However, in other embodiments, the angle at the top
corner 505 may also be equal to 90 degrees or smaller than 90
degrees.
With reference to FIGS. 7-12D, an instrument 60 for use with a
receiving part such as that of the first embodiment is shown, with
respect to details of its distal end section. The instrument 60
includes a tubular holding member 10, which is configured to be
attached to the receiving part 5 and to hold the same in a form-fit
connection. The holding member 10 has two arms 12a, 12b, which are
separated by a slot 18 which extends from a distal end 10a, 10b of
the respective arms. At a distance from the distal end 10a, 10b, a
connecting portion 13 is provided at both sides of the slot 18
(only one side is shown) that connects the arms 12a, 12b together.
The connecting portion 13 has the shape of an arcuate bridge with a
curvature that is concave when viewed from the distal end 10a, 10b.
The thickness of the connecting portion 13 and the curvature is
selected such that the connecting portion 13 acts as a spring
between the arms 12a, 12b. The connecting portion 13 may form a
fulcrum that permits the arms 12a, 12b of the holding member 10 to
perform a pivoting movement like pliers, such that a movement of
the arms 12a, 12b towards each other at a proximal end (not shown)
results in spreading the arms 12a, 12b at the distal end 10a, 10b.
Thereby, an open position of the holding member 10 is defined in
which a receiving part can be inserted between the arms 12a, 12b
adjacent the distal end 10a, 10b. When the arms 12a, 12b are
released at the proximal end (not shown), the return force of the
spring portion moves the arms 12a, 12b towards each other at the
distal end 10a, 10b, whereby a closed position is defined in which
the arms 12a, 12b are substantially parallel to each other.
The tubular holding member 10 has an engagement section 17
extending at the distal end 10a, 10b, and having a generally
cylindrical outer contour with a reduced diameter as compared with
a main section of the tubular holding member 10 to which it is
connected via a conical transition section. The engagement section
17 of the tubular holding member 10 is configured to receive the
receiving part 5 and provides the means for holding the same.
As can particularly be seen in FIG. 8A, the tubular holding member
10 includes substantially cylindrical inner wall portions 16 at
both arms 12a, 12b, wherein a section 16a, 16b of the inner wall
portions 16 within the engagement section 17 are provided with an
increased inner diameter such as to provide a complementary or
mating shape for an upper portion of the receiving part 5. Also,
annular shoulders 161 provided at the proximal end of sections 16a,
16b define an abutment face for the top or first end 5a of the
receiving part 5 when it is inserted into the engagement section 17
of the instrument 60.
With reference to FIGS. 7 and 8B, an engagement recess 14 is formed
as a cutout in sections 16a, 16b of the inner wall portion 16 at
each of the arms 12a, 12b. The engagement recess 14 has a generally
triangular shape with corners 145, 147, 148 and sidewalls 142, 143,
144. As can be seen, tips of the triangular shape are cut off in
order to avoid acute angles at the corners. The position of the
engagement recess 14 within the engagement section 17, and
particularly with respect to the enlarged diameter section 16a of
the inner wall portion 16 and the annular shoulder 161, is such
that when the receiving part 5 is introduced into the inner
accommodation space of the engagement section 17, the projection 50
of the receiving part 5 may be received in the engagement recess 14
of the instrument 60.
With reference to FIGS. 9 and 10, a state is shown wherein a
receiving part 5 (assembled as part of a bone anchoring device) is
received in the inner accommodation space of the engagement section
17 of the tubular holding member 10. As can be seen, the projection
50 is received in the engagement recess 14 of the holding member
10. Similar to the projection 50 of the receiving part 5, the
engagement recess 14 of the instrument 60 has a tapered shape (in
this embodiment: a triangular shape), wherein the taper is oriented
away from the distal end 10a, 10b. The shapes of the engagement
recess 14 and the projection 50 need not be identical, as can be
seen in FIG. 9. Rather, it is sufficient to yield a form-fit
connection between the instrument 60, or holding member 10, and the
receiving part 5 by the mating shapes of the left- and right-side
corners 507, 508 and the sidewall 502 of projection 50 with left-
and right-side corners 147, 148 and sidewall 142 of engagement
recess 14, respectively. Except for some tolerance or play, for
example, as indicated in FIG. 9, the mating shapes of projection 50
and engagement recess 14 (almost) impede further translational
movement in a direction along the central axis C, as well as
rotation about axes C and E.
With reference to FIG. 10, the engagement recess 14 is formed as a
cutout in the inner wall portion 16 of the tubular holding member
10. In other words, the engagement recess 14 is formed by an
aperture, or opening extending through the inner wall portion
towards an outer surface portion of the engagement section 17. This
structure allows amounts of tissue or fluids assembling or
accumulating around the projections 50 to easily escape through the
engagement recess 14 when received therein. Nevertheless, modified
embodiments in which the engagement recess 14 is formed as a groove
within the inner wall portion 16, without extending to the outer
surface portion, are also encompassed by the invention.
With reference to FIGS. 7 and 8A, a guiding channel 15 extends from
the distal end 10a, 10b of each arm 12a, 12b and opens into the
respective engagement recess 14. The guiding channel 15 is formed
within section 16a, 16b of the inner wall portion 16 of the tubular
member 10. The guiding channel 15 includes a substantially flat
bottom surface 151 and two opposing sidewalls 152, and a width of
the guiding channel 15 in a circumferential direction about a
central axis F of the holding member 10 substantially corresponds
to that of the engagement recess 14. It is possible, but not
necessary, that a distance between the sidewalls 152 of the guiding
channel 15 increases towards the distal end 10a, 10b. As can be
seen in FIG. 8A, the bottom surface 151 of the guiding channel 15
is inclined with respect to the central axis F of the holding
member 10. More specifically, the guiding channel 15, or its bottom
surface, is inclined away from the central axis F as the guiding
channel extends towards the distal end 10a, 10b, such that the
mutual distance between, e.g., two opposed guiding channels 15
formed with respect to corresponding engagement recesses 14 at each
of the arms 12a, 12b increases towards the distal end 10a, 10b even
in the closed position. As will be explained below, the guiding
channel 15 facilitates an alignment of the instrument 60 with the
position of the projection 50 of the receiving part 5 during
attachment of the instrument 60 to the receiving part 5.
With reference to FIGS. 11A-11C and 12A-12D, operation of the
instrument 60 and the receiving part 5 during use is explained.
FIGS. 11A and 12A show a first state of attaching the instrument 60
to the receiving part 5. The central axes C, F of the receiving
part 5 and the tubular holding member 10 are manually aligned by
the surgeon, and the instrument is guided to the receiving part
5.
In a second state shown in FIGS. 11B and 12B, the first end 5a of
the receiving part 5 is guided into the accommodation space of the
engagement section 17 until a point wherein the chamfer 506 at the
top corner 505 of projection 50 comes into contact with the bottom
surface of the guiding channel 15. Starting from this point, as can
be seen in FIG. 12C, the chamfer 506 starts to slide on the bottom
surface of guiding channel 15, wherein upon further introduction of
the receiving part into the inner accommodation space of the
engagement section 17, the arms 12a, 12b of the tubular holding
member 10 start to spread and expand, yielding an open position of
the instrument. During further insertion, the inclined sidewalls
503 or 504 may eventually abut on one of the sidewalls of the
guiding channel 15 due to some misalignment of the instrument 60
with respect to the receiving part 5 in the circumferential
direction. Due to the inclination of the sidewalls 503, 504,
however, a rotational force is generated between the instrument and
the receiving part 5, which aligns the instrument with respect to
the receiving part 5. The projection 50 is then smoothly guided
into the guiding channel 15 of the tubular holding member 10 of the
instrument 60.
With reference to FIGS. 11C and 12D, in a third state of operation,
when an edge of the sidewall 502 of projection 50, which faces the
second end 5b of the receiving part 5, passes over the end of the
guiding channel 15, the projection 50 snaps into the engagement
recess 14 of the tubular holding member 10 to establish a form-fit
connection between the receiving part 5 and the instrument 60.
Thereby, the undercut shape of the sidewall 502 further improves
the connection, particularly when the corresponding mating sidewall
142 of the engagement recess 14 is also provided with a surface
that is inclined in an outward direction. Moreover, in addition to
the form-fit connection between the projection 50 and the
engagement recess 14, at the same time when the projection 50 snaps
into the engagement recess 14, the top or first end 5a of the
receiving part 5 abuts on the annular shoulder 161 provided at the
inner wall portion 16 of the tubular holding member 10. As a
consequence, the receiving part 5 is firmly clamped in the inner
accommodation space of the engagement section 17 of the instrument
60.
With reference to FIGS. 13 and 14, a second embodiment of the
present invention is shown. A monoaxial bone anchoring device 200'
includes a receiving part 5' integrally formed with an anchoring
element 1', and a locking element 7. Similar to the first
embodiment, an outer surface portion of the receiving part 5' has a
generally cylindrical contour and a projection 50' is formed at
each of the legs, where the legs are formed by a channel for
receiving a spinal rod 100. The shape, orientation and position of
the projection 50' is almost identical to that of the first
embodiment, i.e., the projection 50' is tapered and narrows in a
direction towards the top or first end 5a. An instrument (not
shown) for use with this receiving part 5' may be the same as that
described above with reference to FIGS. 7-12D. Nevertheless, in
this specific embodiment, the sidewall 502' of the projection 50'
facing the bottom or second end 5b extends radially away from the
central axis C of the receiving part 5', and is not provided with
an undercut.
With reference to FIGS. 15A-15E, modified embodiments of receiving
parts and instruments are shown, respectively. The modifications
mainly refer to the shapes of the projections and engagement
recesses, respectively. In FIG. 15A, the projection 50 and
engagement recess 14 of the first embodiment are repeated for
reference only. In FIG. 15B, the left-side and right-side corners
507'', 508'' of the projection 50'', and the left-side and
right-side corners 147'', 148'' of the engagement recess 14'' are
not cut off as in the first embodiment, but are simply rounded.
With reference to FIG. 15C, the left-side and right-side corners of
each of the projection 50''' and the engagement recess 14''' are
neither cut-off nor substantially rounded, whereas the inclination
of the sidewalls 503''' and 504''' conforms with that of the
sidewalls 143''', 144''' of the engagement recess 14'''. Herein, a
top corner of the projection 50''' is flattened.
With reference to FIG. 15D, the left-side and right-side corners
are rounded, respectively, whereas each of the sidewalls of the
triangular-shaped projection 50'''' and of the engagement recess
14'''' are convexly or concavely curved, and are configured to mate
with each other to provide a form-fit connection. With reference to
FIG. 15E, a structure similar to that shown in FIG. 15C is shown,
but wherein the projection instead comprises two halves 50a''''',
50b''''' being spaced apart, where each half has a bar-like
structure that still maintains the tapered shape of the combined
projection as well as the form-fit connection after snap-in.
Those skilled in the art will readily recognize that various
further modifications in addition to the above-mentioned
modifications are possible and encompassed by the appended
claims.
For example, while in the above embodiments, an arrangement with
one projection at each respective leg of a receiving part is shown,
it is also possible to provide just one projection at one leg of
the receiving part (or beneath), while on the other side (or leg)
another engagement mechanism such as a projection at the instrument
and a recess at the receiving part may be provided, etc.
Further, in the above embodiments, triangular shapes are described
with respect to the projections and engagement recesses,
respectively, when seen in a plan view. However, other shapes may
be encompassed as well, such as oval, semi-circle, trapezoidal,
square/rectangular, diamond, or rhombus shapes, etc., may be
possible as well. Also, other polygonal shapes are encompassed.
Further, the upper surface 501 of the projection has been described
as being flat or following the cylindrical outer contour of the
receiving part. However, a convex, planar, concave, dome, or
cylindrically shaped upper surface may be possible as well, or
analogously to FIG. 15E, a recess can be provided between the outer
side walls of the projection.
Moreover, in the above embodiments, receiving parts having a
generally cylindrical outer contour have been described. However,
the generally cylindrical contour may only apply to partial
sections of the receiving part, while other portions of the
receiving part may be provided with considerably different outer
contours.
In the above embodiments, receiving parts of polyaxial or monoaxial
bone anchoring devices have been described. However, other
receiving parts which are not configured for connection with an
anchoring element for insertion in a bone may also be encompassed
by the invention.
While the present invention has been described in connection with
certain exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments, but is
instead intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the appended
claims, and equivalents thereof.
* * * * *